Prior art logic analyzers provide merely for enabling the storage of input data states in response to a selected number of satisfactions of a single preselected qualifier state condition and for the storage of data states satisfying a second qualifier state condition. While requiring such multiple occurrences in the input data states prior to beginning a "trace" of data states is useful, it does not impose an occurence condition upon states to be stored as part of the actual trace. For both the reasons that memory is limited and that it is desirable to eliminate as much nonrelevant data from the trace as possible to make the analysis thereof less burdensome, it is often desirable to more thoroughly qualify the data stored as part of the trace itself. A useful way of doing this, particularly where loops are involved, is to require that a data state of interest occur a pre-selected number of times before it is stored. Of additional utility in this connection is the ability to restart the entire triggering sequence over upon the occurrence of a designated restart state.
The present invention incorporates multiple triggering circuits of the type described in the referenced patent application entitled DIGITAL PATTERN TRIGGERING CIRCUIT. These triggering circuits provide output signals in response to an input data state satisfying one of the pre-selected qualifier state conditions. A counter and related sequencing logic is coupled to a first set of triggering circuits to determine when the storage of input data states should be enabled. The various pre-selected qualifier state conditions can be required to occur a designated number of times. A separate triggering circuit provides a signal to the sequencing logic for restarting the enabling sequence in response to the detection of a restart state condition. Storage of data states is further qualified by a second set of triggering circuits. The output of this set is supplied to the memory such that only data states meeting one of the pre-selected state conditions are stored.